The first reducing stage of a two-stage regulator generally comprises a metal body in which the pressure reducing device is located. The body has at least one inlet for the compressed air coming from the cylinder or cylinders and a plurality of outlets for the air at a reduced pressure. This device, which is connected to the cylinders, is usually found near the nape of the diver's neck; the diver is, therefore, vulnerable to being struck accidentally by the reducing valve. What is more, the reducing valve itself is in turn exposed to accidental knocks from the underwater environment, for example being struck by rocks or bits of wreckage which can damage it, sometimes even seriously.